Nickel base alloy



July 22, 1969 M A, POHLMAN ETAL 3,457,066

NICKEL BASE ALLOY Filed April l0. 1959 United States Patent() 3,457,066 NICKEL BASE ALLOY Marvin A. Pohlman, Muskegon, Mich., and Joseph B. Moore, Tequesta, Fla., assignors .to General Electric Company, a corporation of New York Filed Apr. 10, 1959, Ser. No. 806,204

Int. Cl. C22c 19/00, 1/10, 1/02 U.S. Cl. 75-171 This invention relates to nickel base alloys' suitable for elevated temperature operation and particularly useful as sheet material. l

Nickel base alloys including relatively wide ranges of cobalt, chromium, molybdenum, titanium and aluminum as their principle alloying elements have been reported as suitable for high temperature use under Conditions ofrelatively high stress. However, the unexpected advantages of a close balance between certain of these elements in narrower ranges had not been completely explored.

It is an object of this invention to provide a nickel base alloy having elevated temperature strength properties greater than presently known alloys for similar applications.

Another object is to provide `a vacuum melted nickel base alloy which in sheet form exceeds the tensile and rupture strengths of known sheet alloys at elevated ternperatures.

According to one form f our alloy, we provide a nickel base sheet alloy comprising in percent by weight Aup to about 0.08 carbon, about 14-17 chromium, about .0.01-

s claims 0.05`boron, about 4-7 molybdenum, about 3-4 titanium,

about 3.6-5 aluminum,about 5-20 cobalt with the balance essentially nickel, impurities and possibly. the usual small amounts of silicon and manganese.

Although .ouralloy in its broad rangehas strength properties` at elevated temperatures greater than those -of other sheet alloys, we prefer our alloy in the range in the percent. by weight of about 0.04-007 carbon, about 14j-15.5. chromium,v about 0025-0035 boron, -about l4.5-l5.5 cobalt,.. about 4.5-5.5 molybdenum, labout:

3,457,066 Patented July 22, 1969 ice FIG. 3 is a graph of the 0.2 percent yield strength and i' of our alloy in its broad range.

rThree of the tests generally conducted on alloys to determine their physical properties are called stress rupture, ultimate tensile "and yield tests, the results of such tests being generally reported as stress rupture strength, ultimate tensile strength and yield strength. Stress rupture strength is the value of stress in pounds per square inch obtained by dividing the amount of an applied load by the area supporting that load initially while the test speciman is maintained at a selected temperature. The strength of material of a test specimen is also to failure under a specied stress and at a specified tem- Ultimate tensile strength is the value in pounds per squareinch obtained when the maximum load recorded during the plastic straining of a specimen is divided by p the cross sectional area of the specimen before straining.

3.3-3.7. titanium, about.4.2-4.6 aluminum with the balance Y essentially nickel impurities,` up to about 0.1 each of manganese and silicon and a maximum of about 0.2 iron.

Our sheet alloy in its lower range ofcobalt after a heat treatment, such as heating at' about 2100 F. for about one half hour, air cooling,lheati'r'1`g at about 1400" FL for about sixteen (16) hours 'and then air cooling,"is characterized by particularly high elevated. temperaturertensile strength; in its upper range of 'cobalt it has exceptionally high elevated temperature stress rupture strength after that same type of heat treatment. We prefer about 14.5- 15.5 percent by weight cobalt because that range results in the best balance at elevated temperatures between such properties as tensile and rupture strengths, oxidation resistance and the ability ofthe sheet material to be formed or worked.

Although the scope of our invention will be pointed out in the claims, our alloy will be better understood from our description taken in connection with the accompanyin drawing in which:

FIG. l is a graph of the average stress rupture life of our preferred sheet alloy compared with the strongest of other available sheet alloys;

FIG. 2 is a graph of the ultimate tensile strength band of our alloy in its broad range;

The term 0.2% vyield strength shown in FIG. 3 is the stress at which a material exhibits 0.2% deviation from the proportionality of stress to strain. This figure, sometimes referred to as 0.2% offset is commonly used as the basis of design strength of articles.

The nominal chemical compositions of alloy A referred toin FIGS.. l-3 and.of.alloy B .referred-to in FIG. -l are given in the following table along with the composition range of our alloy all prepared by vacuum melting tech` niques.

TABLE I Y Y Composition in percent by weight (sheet material).

otirAuoy ..-....Bo'rti Preferred. .i

range A range Alloy A Alloy B ,l una,` .o4-.o7 .1 l ..1v 14-17l `its-5:5 f y19` 15.5 .0i-.o5y ...oas-.035 .nos 1.00.5 5-20 11s-15.5 ,l 4-1 4.95.5 V`1o 5.5 .34, `3.3-3.7 3,-1 g f2.5 .ae-,5 ,4.2-4.6 1.1 z

.15# 1o Bal. Bal. Bal. Bal. Si (max.) 1 1 .5 1. Mn (max.) .1 .1 .5 .1

1 Max.

Referring to FIG. 1, the stress rupture strengths of the alloys after heat treatment are represented by the comparison of stress with a time-temperature parameter shown at the horizontal coordinate. This parameter, known as the Larson-Miller parameter, has been calculated from rthe Formula P=T (20-Hog t) 103 in which P equals the time-temperature parameter number, T equals absolute temperature in degrees Rankine and t equals the time in hours. The curves of FIG. l have been prepared from a large amount of stress rupture test results and represent a compact summary of a wide range of data. Using this special graph, it is possible to predict the stress rupture life of a material under a given load at a given temperature.

The curves of FIG. 1 show that the stress rupture strength of our vacuum melted sheet alloy in its preferred range is greater than that of the two strongest sheet alloys available, each after heat treatment.

The results of strength data represented by the graphs of FIGS. 2 and 3 show that our heat treated vacuum melted sheet alloy in its broad range has greater elevated temperature ultimate tensile strength and 0.2% yield strength than the next strongest available heat treated alloy represented by alloy A.

A comparison of the chemistry of alloy A with that of our alloy indicates that unexpected results have been achieved by our careful study and selection of elements previously reported in relatively broad ranges.

EXAMPLE 1 TABLE II Stress rupture lite Temperature F.) Stress (1,000 p.s.i.) (hours) A Series of sheet materials of the compositions shown in Table III were to a thickness of about 0.065 inch and heat treated as in Example 1. The compositions are 1n percent by weight.

TABLE III Example N o. 2 3 4 5 06 06 06 06 4. 54 4. 54 4. 47 4. 47 3. 55 3. 55 3. 53 3. 53 4. 91 4. 91 5. 07 5. 07 14. 57 14. 57 14. 68 14. 68 4. 6 9. 4 14. 8 19. 0 0. 12 0.12 0.09 0.09 0. 07 0. 07v 0. 05 0. 05 0. 0. 05 0. 05 0. 05 0. 027 0. 027 0. 031 0. 031 Bal. l Bal. Bal. Bal.

The results of tensile testing these materials, as tabulated in Table IV, show thatl although the entire range of our alloy as represented `graphically in FIGS. 2 and 3 are higher in tensile strength than that of the strongest available alloy A, the range of cobalt Vbetween about 5-15 percent generally appears to be stronger.

TABLE IV Ultimate tensile 0.2% yield strength Temp. F.) Example No. strength (1,000 (1,000 p.s.i.)

What we claim as new and desire to secure by Letters Patent of the United States is: j

1.'A wrought nickel base alloy consisting of in percent by weight about 0.04-0.07 carbon, about 14.5-15.5 chromium, about 0025-0035 boron about 14.5-15.5 cobalt, about 4'.5-5.5 molybdenum, about 3.3-3.7 titanium, about 4.2-4.6 aluminum, with the balance nickel and impurities.

2. The alloy of claim 1 consisting in additions in percent by weight up to about 0.1 silicon and up to about 0.1 manganese. i

3. A wrought nickel base alloy consisting of in percent by weight about 0.06 carbon, about l5 chromium, about 0.03 boron, about 15 cobalt, about 5 molybdenum, about 3.5 titanium, about 4.5 aluminum, with the balance nickel and impurities.

4. A nickel base alloy consisting of in percent -by weight, 14.5-l5.5 chromium, l4.5-l5.5 cobalt, 3.3-3.7 titanium, 4.2-4.5 alumium, .025-.035 boron, 4.5-5.5 molybdenum vand the balance nickel.

5. A nickel base alloy consisting essentially of from 14.0% to 17.0% chromium, from 13.0% to 20.0% cobalt, from 3.25% to 3.75% titanium, from 4.0% to 4.5% aluminum, from 0.02% to 0.04% boron and from 4.50% to 5.50% molybdenum, the balance Ibeing essentially all nickel.

References Cited UNITED STATES PATENTS 2,570,194 10/1951 Bieber etal 14S-21.9 2,712,498 7/ 1955 Gresham et al. 75-171 2,809,110 10/ 1957 Darmara 75-171 2,688,536 9/1954 Callaway et al. 75-171 2,860,968 11/ 1958 Boegehold et al. 75-171 2,920,956 1/ 1960 Nisbet et al. 75-171 2,977,222 3/ 1961 Bieber -75-171 FOREIGN PATENTS 92,627 10/ 1958 Norway.

548,778 11/ 1957 Canada. 561,928 11/1957 Belgium.

814,029 5/ 1959 Great Britain.

RICHARD o. DEAN, Primary Examiner Dedication 3,457,066.-.l[m'^vin A. Pohlman, Muskegon, Mich., and ,lmnp/L B. Moore, Te uesta, Fla. NICKEL BASE ALLOY. Patent dated July 22 1969. Detclicaton fled June 26, 1970, by the assignee, General Eectrz'c Company. Hereby dedicates the remaining term of said patent to the Public.

[Oficial Gazette November 10, 1970.] 

5. A NICKEL BASE ALLOY CONSISTING ESSENTIALLY OF FROM 14.0% TO 17.0% CHROMIUM, FROM 13.0% TO 20.0% COBALT, FROM 3.25% TO 3.75% TITANIUM, FROM 4.0% TO 4.5% ALUMINUM, FROM 0.02% TO 0.04% BORON AND FROM 4.50% TO 5.50% MOLYBDENUM, THE BALANCE BEING ESSENTIALLY ALL NICKEL. 